By late summer, the plants have seized all the sustenance they can from air and earth. Winds scatter seed from grasses turned scarlet, rust, even lavender. The goldenrod finally lives up to its name.

Photograph by Jim Richardson

Written by Verlyn Klinkenborg

Republished from the pages of National Geographic magazine

Americans have always lived in a land of possibility—a place where the grass is "hopeful green stuff," as the poet Walt Whitman put it. Our habit is to wonder what we can make of a place, to gaze at the future instead of the present. As a result, nature often lies hidden beneath our expectations.

That's why the Flint Hills of Kansas—the last great swath of tallgrass prairie in the nation—can be so hard to grasp. The Flint Hills are no longer hard to get to, no longer a matter of ox train and overland trail from somewhere east of the Missouri River. They're transected by roads of every description now. But when you get to the hills,when you rise onto the low shield of flint and limestone that defines them and walk up onto the highest brow and stand into the wind that's trying to pry your ears apart, what do you see?

Open sky, open land, unending horizon, the "limitless and lonesome prairie," to quote Whitman again. But the word that also springs to mind may be "nothing." A glorious nothing, but nothing nonetheless.

That too is an American word, full of the conviction that nothing much stands between herds of bison and herds of cattle, between the millions of acres of tallgrass prairie that once stretched across the plains and the millions of acres of corn and soybeans growing there now. Historically, we have valued the prairie grasses mainly as cattle fodder or as placeholders till the sod could be broken and crops planted, crops that are themselves just placeholders until the houses eventually come. The prairie topography is almost too subtle for us, which may be one reason the National Park System contains only a single unit dedicated to grassland—the Tallgrass Prairie National Preserve in Chase County, Kansas, the heart of the Flint Hills.

When you walk across the grassbound hills above Fox creek, just northwest of the small town of Strong City, it's easy to pretend you're striding through the past. There is no sound or sight to remind you of the immediate century. But that reverie too is a way of failing to notice the grassland. The hard part here in the Flint Hills—and in any of the few remaining patches of native prairie—is learning to see the tallgrass ecosystem for itself. It is a study in the power of modesty. Learn it well enough and you begin to suspect that grasses are what hold this world together.

Some of the lowlands in the Flint Hills are planted to corn and milo, and the creek bottoms are full of oaks and an occasional white-limbed sycamore. Along the gravel roads you come across old limestone fences and Osage orange trees, or bois d'arc, planted by the settlers as hedge and windbreak. But on the uplands—and the Flint Hills are mostly upland, stretching from northern Kansas down into Oklahoma—the prairie still holds its own. The soils are too thin, too rock-strewn to make good farmland. Wherever you walk, you find drifts of limestone, like fallen grave markers, grass pushing through the holes that time has made in that soluble stone. The very toughness of this place—amply recorded by its early occupants—has helped preserve it.

That toughness is more than mirrored in the grasses themselves, especially in species like big bluestem—one of the dominant grasses in the Flint Hills. Big bluestem (Andropogon gerardii) persists from year to year, spreading by seed and rhizome, creating an underground web of coarse roots near the surface as well as fine root fibers that may reach eight feet deep where the soil allows. What grows above ground—the tillers—is essentially disposable. The actual growing tip of the plant lies low to the earth in spring and is undisturbed when the tillers are cropped or singed. Like most of the other plants in the tallgrass ecosystem, big bluestem actually rejoices in grazing and fire, if they come at the right time of the year.

The prairie is sometimes called a sea of grass—a metaphor that points to the endless green expanse and the wavelike motion of the grasses. But if there is also a tide in these grasslands—a cycle of growth that sweeps chronologically across the Flint Hills. High tide comes early in the year. The prairie swells into life in early spring, and if fire comes then, the plants respond with a redoubled burst of growth. The fires clear away last year's plant debris, letting in more light and warming the soil.

To the grazers on the hills—bison once and cattle now—the new green on blackened ground is a timely feast. In the cycle of warm-season grasses like big bluestem, this is the peak of their nutritional richness. They continue to grow all through the summer, but as the weeks pass they harden off until, in autumn, their leaves are somber, dried remnants of themselves, crimson, maroon, clattering in the wind.

In most of America, agriculture has meant replacing the incredible complexity of a natural ecosystem with the incredible simplicity of a single crop growing on bare ground. And almost everywhere, fire was the first thing banished, hunted down as relentlessly as if it were a sheep-killing wolf. But in the Flint Hills fire still thrives because the ranchers here depend on a natural ecosystem. Even in the mid-19th century, cattlemen understood that the richness of the Flint Hills grasses depended on a good spring burn—something they learned from the Native Americans they displaced. And so, early each April—even as the cattle that will grace down the prairie are shipping in—the hills go up in smoke.

The balance isn't perfect, of course. Without human intervention, the Flint Hills would burn more randomly than they do now, creating a broader range of habitats than frequent burns allow. Annual burning may suppress some species—including prairie-chickens, whose numbers have plummeted—that might flourish in the more complicated tangle of grasses. There is also a worrying trend toward ground and aerial spraying to control a highly invasive weed called sericea lespedeza, introduced decades ago to curb erosion around mines and provide forage and cover for wildlife around reservoirs.

And yet the Flint Hills is one of the few places in the United States where the prevailing agricultural system works essentially in tandem with an ancestral native ecosystem, preserving most of its complexity and the dynamic processes that helped shape it. First comes the fire, then for a few months the cattle—intensively stocked—and then the hills are left to themselves.

The springtime sacrifice of grasses does more than fatten steers. It is the prairie's only defense against woods and heavy brush. Wherever the range fires have lapsed, trees begin to move in, especially the eastern red cedar. Deep in the tallgrass, it is hard to imagine that this lush growth cannot hold its own against woody species. The prairie seems so durable, so all-encompassing. And yet the prarie is the natural habitat of fire. So far, the way the land has been settled—sparsely and mostly in the bottomland—leaves room for the flames of spring to sweep unchecked across the upland horizon.

In the Flint Hills, you instinctively feel that the prairie is for looking outward. But to see it truly, you have to look downward, past the seedheads of switchgrass and stiff goldenrod, and down into the roots. This is not just an act of imagination. Here and there, you come across the cutbank of a shallow stream, and you can glimpse in the exposed earth an unraveling skein of tough fibers working their way downward. It's enough to make you doubt the priority of what grows upward. The grass leaves and stems and inflorescences seem to exist to serve the roots, rather than the other way around.

The Flint Hills lie at the western edge of a prairie ecosystem, and except in wet, sheltered spots, the tallgrass species here grow much shorter than they do farther east. In late summer, walking through a patch of restored Illinois prairie, you can almost imagine the scale of the root system, because it is mirrored in the head-high plants all around you. But here the prairie is surprisingly asymmetrical. The late-summer grasses and forbs, burned and grazed earlier in the year, rarely stand more than knee-high. They give no hint of what lies beneath them.

Even the cutbank does not reveal the mass and density of the roots pushing beneath the prairie surface. But imagine the prairie upside down—the leaves and stems growing downward into the soil and the roots of all these species growing skyward. You are suddenly walking through a dense, tenacious thicket of roots. The horizon is gone because you are over-ears in plant fibers, some spreading and slender, some tall, with strange bulbous growths on them. It is as though you were walking through a forest of veins and capillaries, each species finding a different niche—a different height, a different strategy—in the competition for resources.

This image alone cannot convey how tightly the prairie roots—rightside down—grasp the soil into which they have plunged, how closely they bind the earth and sky. Part of the pleasure of walking through the Flint Hills is sensing that coherence underfoot, the way the prairie roots have woven the soil together and anchored a stunningly diverse community above and below the soil line.

Just how the prairie speaks to you depends on who you are. Some will find it full of nothing or full, at best, of cattle fodder and copious views. But like any ecosystem that remains more than a shadow of itself, the tallgrass prairie reminds us how we should think about the life that surrounds us. Spring brings the fires, the solid hopeful green of new grass, the booming of mating prairie-chickens in the Flint Hills. Our old habits of seeing find in all of this a familiar simplicity, the kind you push past on your way to a more human future. But in the ancient prairie itself—in its diversity, its coherence, its community, its capacity for regeneration—there is a new way of seeing waiting to be found.